Method for mapping a tubular region near the heart

ABSTRACT

A method is provided for mapping electrical activity within a tubular region of or near the heart having a inner circumference, such as a pulmonary vein. The method comprises inserting into the heart a distal end of a mapping catheter. The mapping catheter comprises an elongated tubular catheter body having an outer wall, proximal and distal ends, and at least one lumen extending therethrough. The catheter includes a mapping assembly comprising a tubular structure comprising a pre-formed generally circular main region generally transverse and distal to the catheter body and having an outer circumference. The tubular structure comprises a non-conductive cover over at least the main region of the mapping assembly. A plurality of electrode pairs, each comprising two ring electrodes, are carried by the generally circular main region of the mapping assembly. The method further comprises contacting the outer circumference of the generally circular main region with the inner circumference of the tubular region and mapping the electrical activity within the tubular region with the electrodes along the generally circular main region.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional of U.S. application Ser. No.09/943,546, filed Aug. 30, 2001, which is a continuation-in-part of U.S.application Ser. No. 09/551,467, filed Apr. 17, 2000,which claims thebenefit of U.S. Provisional Application No. 60/178,478, filed Jan. 27,2000, the entire disclosures of which are incorporated herein byreference.

FIELD OF THE INVENTION

[0002] The present invention relates to a method for mapping a tubularregion of or near the heart, and more particularly, a method for mappingthe pulmonary vein.

BACKGROUND OF THE INVENTION

[0003] Atrial fibrillation is a common sustained cardiac arrhythmia anda major cause of stroke. This condition is perpetuated by reentrantwavelets propagating in an abnormal atrial-tissue substrate. Variousapproaches have been developed to interrupt wavelets, including surgicalor catheter-mediated atriotomy. Prior to treating the condition, one hasto first determine the location of the wavelets. Various techniques havebeen proposed for making such a determination. None of the proposedtechniques, however, provide for measurement of the activity within apulmonary vein, coronary sinus or other tubular structure about theinner circumference of the structure.

SUMMARY OF THE INVENTION

[0004] A method is provided for mapping electrical activity within atubular region of or near the heart having an inner circumference, suchas a pulmonary vein. The method comprises inserting into the heart adistal end of a mapping catheter. The mapping catheter comprises anelongated tubular catheter body having an outer wall, proximal anddistal ends, and at least one lumen extending therethrough. The catheterincludes a mapping assembly comprising a tubular structure comprising apre-formed generally circular main region generally transverse anddistal to the catheter body and having an outer circumference. Thetubular structure comprises a non-conductive cover over at least themain region of the mapping assembly. A plurality of electrode pairs,each comprising two ring electrodes, are carried by the generallycircular main region of the mapping assembly. The method furthercomprises contacting the outer circumference of the generally circularmain region with the inner circumference of the tubular region andmapping the electrical activity within the tubular region with theelectrodes along the generally circular main region.

DESCRIPTION OF THE DRAWINGS

[0005] These and other features and advantages of the present inventionwill be better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings wherein:

[0006]FIG. 1 is a side cross-sectional view of an embodiment of thecatheter of the invention.

[0007]FIG. 2 is a side cross-sectional view of a catheter body accordingto the invention, including the junction between the catheter body andintermediate section.

[0008]FIG. 3 is a cross-sectional view of the intermediate section,including the junction between the intermediate section and the mappingassembly.

[0009]FIG. 4 is a schematic perspective view of the mapping assemblyaccording to the invention.

[0010]FIG. 5 is a side view of the mapping assembly according to theinvention in a clockwise formation.

[0011]FIG. 6 is a side view of the mapping assembly according to theinvention in a counterclockwise formation rotated 90° relative to theassembly depicted in FIG. 5.

[0012]FIG. 7 is a schematic view of the mapping assembly according tothe invention.

[0013]FIG. 8 is a schematic view of the mapping assembly according tothe invention depicting the relationship between the first and lastelectrodes.

[0014]FIG. 9 is a schematic view of an alternative mapping assemblyaccording to the invention.

DETAILED DESCRIPTION

[0015] In a particularly preferred embodiment of the invention, there isprovided a catheter having a mapping assembly at its distal end. Asshown in FIG. 1, the catheter comprises an elongated catheter body 12having proximal and distal ends, a intermediate section 14 at the distalend of the catheter body, a control handle 16 at the proximal end of thecatheter body, and a mapping assembly 17 mounted at the distal end ofthe catheter to the intermediate section.

[0016] With reference to FIG. 2, the catheter body 12 comprises anelongated tubular construction having a single, axial or central lumen18. The catheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. A presentlypreferred construction comprises an outer wall 20 made of polyurethaneor PEBAX. The outer wall 20 comprises an imbedded braided mesh ofstainless steel or the like to increase torsional stiffness of thecatheter body 12 so that, when the control handle 16 is rotated, theintermediate section 14 of the catheter 10 will rotate in acorresponding manner.

[0017] The outer diameter of the catheter body 12 is not critical, butis preferably no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 20 is not critical, but is thinenough so that the central lumen 18 can accommodate a puller wire, leadwires, and any other desired wires, cables or tubes. If desired, theinner surface of the outer wall 20 is lined with a stiffening tube (notshown) to provide improved torsional stability. A particularly preferredcatheter has an outer wall 20 with an outer diameter of from about 0.090inch to about 0.94 inch and an inner diameter of from about 0.061 inchto about 0.065 inch.

[0018] The intermediate section 14 comprises a short section of tubing22 having three lumens. The first lumen 30 electrode carries lead wires50, the second lumen 32 carries a puller wire 64, and the third lumen 34carries a support member 24. The tubing 22 is made of a suitablenon-toxic material that is preferably more flexible than the catheterbody 12. A presently preferred material for the tubing 22 is braidedpolyurethane, i.e., polyurethane with an embedded mesh of braidedstainless steel or the like. The size of each lumen is not critical, butis sufficient to house the lead wires, puller wire or support member.

[0019] The useful length of the catheter, i.e., that portion that can beinserted into the body excluding the mapping assembly 17, can vary asdesired. Preferably the useful length ranges from about 110 cm to about120 cm. The length of the intermediate section 14 is a relatively smallportion of the useful length, and preferably ranges from about 3.5 cm toabout 10 cm, more preferably6 from about 5 cm to about 6.5 cm.

[0020] A preferred means for attaching the catheter body 12 to theintermediate section 14 is illustrated in FIG. 2. The proximal end ofthe intermediate section 14 comprises an outer circumferential notch 26that receives the inner surface of the outer wall 22 of the catheterbody 12. The intermediate section 14 and catheter body 12 are attachedby glue or the like.

[0021] If desired, a spacer (not shown) can be located within thecatheter body between the distal end of the stiffening tube (ifprovided) and the proximal end of the intermediate section. The spacerprovides a transition in flexibility at the junction of the catheterbody and intermediate section, which allows this junction to bendsmoothly without folding or kinking. A catheter having such a spacer isdescribed in U.S. Pat. No. 5,964,757, the disclosure of which isincorporated herein by reference.

[0022] At the distal end of the intermediate section 14 is a mappingassembly, as shown in FIGS. 3 to 7. The mapping assembly is formed fromthe distal end of the support member 24 covered by a non-conductivecovering 28. The mapping assembly comprises a generally straightproximal region 38, a generally circular main region and a generallystraight distal region 40. The proximal region 38 is mounted on theintermediate section 14, as described in more detail below, so that itsaxis is generally parallel to the axis of the intermediate section. Theproximal region 38 preferably has an exposed length, e.g., not containedwithin the intermediate section 14, ranging from about 3 mm to about 12mm, more preferably about 3 mm to about 8 mm, still more preferablyabout 5 mm inch, but can vary as desired.

[0023] The generally circular main region 39 does not form a flatcircle, but is very slightly helical, as shown in FIGS. 4 to 6. The mainregion 39 has an outer diameter preferably ranging to about 10 mm toabout 25 mm, more preferably about 12 mm to about 20 mm, still morepreferably about 15 mm. The transition region 41 of the straightproximal region 38 and generally circular main region 39 is slightlycurved and formed such that, when viewed from the side with the proximalregion at the top of the circular main region as shown in FIG. 5, theproximal region (along with the intermediate section 14) forms an angleα with the curved region ranging from about 75° to about 95°, preferablyfrom about 83° to about 93°, more preferably about 87°. The main region39 can curve in a clockwise direction, as shown in FIG. 5, or acounterclockwise direction, as shown in FIG. 6. When the assembly 17 isturned 90°, as shown in FIG. 6, so that the transition region 41 is nearthe center of the main region, the proximal region (along with theintermediate section 14) forms an angle β with the main region rangingfrom about 90° to about 135°, preferably from about 100° to about 110°,more preferably about 105°.

[0024] The support member 24 is made of a material having shape-memory,i.e., that can be straightened or bent out of its original shape uponexertion of a force and is capable of substantially returning to itsoriginal shape upon removal of the force. A particularly preferredmaterial for the support member 24 is a nickel/titanium alloy. Suchalloys typically comprise about 55% nickel and 45% titanium, but maycomprise from about 54% to about 57% nickel with the balance beingtitanium. A preferred nickel/titanium alloy is Nitinol, which hasexcellent shape memory, together with ductility, strength, corrosionresistance, electrical resistivity and temperature stability. Thenon-conductive covering 28 can be made of any suitable material, and ispreferably made of a biocompatible plastic such as polyurethane or PEBAX

[0025] A series of ring electrodes 36 are mounted on the non-conductivecovering 28 of the generally circular main region 39 of the mappingassembly 17. The ring electrodes 36 can be made of any suitable solidconductive material, such as platinum or gold, preferably a combinationof platinum and iridium, and mounted onto the non-conductive covering 28with glue or the like. Alternatively, the ring electrodes can be formedby coating the non-conductive covering 28 with an electricallyconducting material, like platinum, gold and/or iridium. The coating canbe applied using sputtering, ion beam deposition or an equivalenttechnique.

[0026] In a preferred embodiment, each ring electrode 36 is mounted byfirst forming a hole in the non-conductive covering 28. An electrodelead wire 50 is fed through the hole, and the ring electrode 36 iswelded in place over the lead wire and non-conductive covering 28. Thelead wires 50 extend between the non-conductive covering 28 and thesupport member 24. The proximal end of each lead wire 50 is electricallyconnected to a suitable connector 37, which is connected to a source ofRF energy (not shown).

[0027] The number of ring electrodes 36 on the assembly can vary asdesired. Preferably the number of ring electrodes ranges from about sixto about twenty, preferably from about eight to about twelve. In aparticularly preferred embodiment, the assembly carries ten ringelectrodes. The ring electrodes 36 are preferably approximately evenlyspaced around the generally circular main region 39, as best shown inFIG. 7. In a particularly preferred embodiment, a distance ofapproximately 5 mm is provided between the centers of the ringelectrodes 36.

[0028]FIGS. 7 and 8 show a particularly preferred electrode arrangement.As explained above, the generally circular main region 39 is veryslightly helical, although FIGS. 7 and 8 depict the main region as aflat circle, as it would generally appear when viewed from the distalend of the catheter. The generally straight distal region 40 forms atangent relative to the generally circular main region 39 and contactsthe main region at a tangent point 43. A first electrode 36 a isprovided, which is the electrode that is on the generally circular mainregion 39 closest to the proximal region 38. A second electrode 36 b isprovided, which is the electrode that is on the generally circular mainregion 39 closest to the distal region 40. Preferably, the firstelectrode 36 a is positioned along the circumference of the generallycircular main region 39 at a distance θ of no more than about 55° fromthe tangent point, more preferably no more than about 48° from thetangent point, still more preferably from about 15° to about 36° fromthe tangent point. Preferably the second electrode 36 b is positionedalong the circumference of the generally circular main region 39 at adistance ω of no more than about 55° degrees from the tangent point,more preferably no more than about 48° from the tangent point, stillmore preferably from about 15° to about 36° from the tangent point.Preferably the first electrode 36 a is positioned along thecircumference of the generally circular main region 39 at a distance γof no more than 100° from the second electrode 36 b, preferably no morethan 80° from the second electrode, still more preferably from about 30°to about 75° from the second electrode.

[0029] An alternative electrode arrangement is depicted in FIG. 9. Inthis embodiment, the mapping assembly includes a series of ringelectrode pairs 35. Each ring electrode pair 35 comprises twoclosely-spaced ring electrodes 36. As used herein, the term “ringelectrode pair” refers to a pair of ring electrodes that are arrangedcloser to each other than they are to the other adjacent ringelectrodes. Preferably the distance between two electrodes 36 of anelectrode pair 35 is less than about 3 mm, more preferably less thanabout 2 mm, still more preferably from about 0.5 mm to about 1.5 mm. Thenumber of electrode pairs 35 can vary as desired, and preferably rangesfrom 6 to 14 pairs, more preferably 10 pairs.

[0030] In a particularly preferred embodiment, the mapping assemblycarries 10 pairs of electrodes with a space of approximately 1 mmbetween the two electrodes 36 of each pair 35. Preferably each ringelectrode 36 is relatively short, having a length ranging from about 0.4mm to about 0.75 mm, with the most distal ring electrode 36 c beinglonger than the other ring electrodes, preferably having a lengthranging from about 1 mm to about 1.5 mm. The longer ring electrodeprovides a signal to the user when the catheter is being viewed underfluoroscopy. Specifically, because the mapping assembly is generallycircular, it can be difficult for the user to determine which electrodesare placed at a particular location in the heart. By having one ringelectrode, such as the most distal ring electrode, sized differentlyfrom the other ring electrodes, the user has a reference point whenviewing the catheter under fluoroscopy.

[0031] Regardless of the size and number of the ring electrodes 36, theelectrode pairs 35 are preferably approximately evenly spaced around thegenerally circular main region 39. The closely-spaced electrode pairs 35allow for more accurate detection of near field pulmonary vein potentialversus far field atrial signals, which is very important when trying totreat atrial fibrillation. Specifically, the near field pulmonary veinpotentials are very small signals whereas the atria, located very closeto the pulmonary vein, provides much larger signals. Accordingly, evenwhen the mapping array is placed in the pulmonary vein, it can bedifficult for the physician to determine whether the signal is a small,close potential (from the pulmonary vein) or a larger, farther potential(from the atria). Closely-spaced bipoles permit the physician to moreaccurately determine whether he is looking at a close signal or a farsignal. Accordingly, by having closely-spaced electrodes, one is able totarget exactly the locations of myocardial tissue that have pulmonaryvein potentials and therefore allows the clinician to deliver therapy tothe specific tissue. Moreover, the closely-spaced electrodes allow thephysician to determine the exact anatomical location of the ostium bythe electrical signal.

[0032] If desired, additional electrodes (not shown) could be mountedalong the intermediate section 14, the generally straight proximalsection 39, the transition region 41, and generally straight distalregion 40.

[0033] The generally straight distal region 40 is provided with anatraumatic design to prevent the distal end of the mapping assembly 17from penetrating tissue. In the depicted embodiment, the distal region40 comprises a tightly wound coil spring 44 made, for example, ofstainless steel, such as the mini guidewire commercially available fromCordis Corporation (Miami, Fla.) or a coil having a 0.0045 inch wiresize and a 0.009 inch inner diameter, such as that commerciallyavailable from Microspring. The coil spring 44 is mounted at itsproximal end in a short piece of tubing 45 with polyurethane glue or thelike, which is then glued or otherwise anchored within thenon-conductive covering 28. The tubing 45 is less flexible than thenon-conductive covering 28 but more flexible than that support member 24to provide a transition in flexibility along the length of the mappingassembly 17. The distal end of the distal region 40 is capped,preferably with polyurethane glue 46, to prevent body fluids fromentering the mapping assembly 17. In the depicted embodiment, thegenerally straight distal region 40 has a length of about 0.5 inch, butcan be any desired length, for example, ranging from about 0.25 inch toabout 1.0 inch. The generally straight distal region 40 is preferablysufficiently long to serve as an anchor for introducing the catheterinto a guiding sheath, as discussed in more detail below, because themapping assembly 17 must be straightened upon introduction into thesheath. Without having the generally straight distal region 40 as ananchor, the mapping assembly 17 has a tendency to pull out of theguiding sheath upon its introduction into the guiding sheath. Any otheratraumatic tip design that prevents the distal end of the mappingassembly from penetrating tissue could be provided. An alternativedesign in the form of a plastic ball is described in copending patentapplication Ser. No. 09/370,605, entitled “ATRIAL BRANDING IRON CATHETERAND METHOD FOR TREATING ATRIAL FIBRILLATION”, the entire disclosure ofwhich is incorporated herein by reference. Additionally, if desired, thedistal region 40 can be formed, at least in part, of a radiopaquematerial to aid in the positioning of the mapping assembly 17 underfluoroscopy.

[0034] The junction of the intermediate section 14 and mapping assembly17 is shown in FIG. 3. The non-conductive covering 28 is attached to thetubing 22 of the intermediate section by glue or the like. The supportmember 24 extends from the third lumen 32 into the non-conductivecovering 28. The proximal end of the support member 24 terminates ashort distance within the third lumen 32, approximately about 5 mm, soas not to adversely affect the ability of the intermediate section 14 todeflect. However, if desired, the proximal end of the support member 24can extend into the catheter body 12.

[0035] The lead wires 50 attached to the ring electrodes 36 extendthrough the first lumen 30 of the intermediate section 14, through thecentral lumen 18 of the catheter body 12, and the control handle 16, andterminate at their proximal end in the connector 37. The portion of thelead wires 50 extending through the central lumen 18 of the catheterbody 12, control handle 16 and proximal end of the intermediate section14 are enclosed within a protective sheath 62, which can be made of anysuitable material, preferably polyimide. The protective sheath 62 isanchored at its distal end to the proximal end of the intermediatesection 14 by gluing it in the first lumen 30 with polyurethane glue orthe like.

[0036] The puller wire 64 is provided for deflection of the intermediatesection 14. The puller wire 64 extends through the catheter body 12, isanchored at its proximal end to the control handle 16, and is anchoredat its distal end to the intermediate section 14. The puller wire 64 ismade of any suitable metal, such as stainless steel or Nitinol, and ispreferably coated with Teflon® or the like. The coating impartslubricity to the puller wire 64. The puller wire 64 preferably has adiameter ranging from about 0.006 to about 0.010 inch.

[0037] A compression coil 66 is situated within the catheter body 12 insurrounding relation to the puller wire 64. The compression coil 66extends from the proximal end of the catheter body 12 to the proximalend of the intermediate section 14. The compression coil 66 is made ofany suitable metal, preferably stainless steel. The compression coil 66is tightly wound on itself to provide flexibility, i.e., bending, but toresist compression. The inner diameter of the compression coil 66 ispreferably slightly larger than the diameter of the puller wire 64. TheTeflon® coating on the puller wire 64 allows it to slide freely withinthe compression coil 66. The outer surface of the compression coil 66 iscovered by a flexible, non-conductive sheath 68, e.g., made of polyimidetubing.

[0038] The compression coil 66 is anchored at its proximal end to theouter wall 20 of the catheter body 12 by proximal glue joint 70 and atits distal end to the intermediate section 14 by distal glue joint 72.Both glue joints 70 and 72 preferably comprise polyurethane glue or thelike. The glue may be applied by means of a syringe or the like througha hole made between the outer surface of the catheter body 12 and thecentral lumen 18. Such a hole may be formed, for example, by a needle orthe like that punctures the outer wall 20 of the catheter body 12 whichis heated sufficiently to form a permanent hole. The glue is thenintroduced through the hole to the outer surface of the compression coil66 and wicks around the outer circumference to form a glue joint aboutthe entire circumference of the compression coil.

[0039] The puller wire 64 extends into the second lumen 32 of theintermediate section 14. Preferably the puller wire 64 is anchored atits distal end to the distal end of the intermediate section 14, asshown in FIG. 3. Specifically, a T-shaped anchor is formed, whichcomprises a short piece of tubular stainless steel 80, e.g., hypodermicstock, which is fitted over the distal end of the puller wire 64 andcrimped to fixedly secure it to the puller wire. The distal end of thetubular stainless steel 80 is fixedly attached, e.g., by welding, to across-piece 82 formed of stainless steel ribbon or the like. Thecross-piece 82 sits beyond the distal end of the second lumen 32. Thecross-piece 82 is larger than the lumen opening and, therefore, cannotbe pulled through the opening. The distal end of the second lumen 32 isthen filled with glue or the like, preferably a polyurethane glue.Within the second lumen 32 of the intermediate section 14, the pullerwire 64 extends through a plastic, preferably Teflon®, puller wiresheath (not shown), which prevents the puller wire 64 from cutting intothe wall of the intermediate section 14 when the intermediate section isdeflected.

[0040] Longitudinal movement of the puller wire 42 relative to thecatheter body 12, which results in deflection of the intermediatesection 14, is accomplished by suitable manipulation of the controlhandle 16. Examples of suitable control handles for use in the presentinvention are disclosed, for example, in U.S. Pat. Nos. Re 34,502 and5,897,529, the entire disclosures of which are incorporated herein byreference.

[0041] In use, a suitable guiding sheath is inserted into the patientwith its distal end positioned at a desired mapping location. An exampleof a suitable guiding sheath for use in connection with the presentinvention is the Preface™ Braiding Guiding Sheath, commerciallyavailable from Cordis Webster (Diamond Bar, Calif.). The distal end ofthe sheath is guided into one of the atria. A catheter in accordancewith the present invention is fed through the guiding sheath until itsdistal end extends out of the distal end of the guiding sheath. As thecatheter is fed through the guiding sheath, the mapping assembly 17 isstraightened to fit through the sheath. Once the distal end of thecatheter is positioned at the desired mapping location, the guidingsheath is pulled proximally, allowing the deflectable intermediatesection 14 and mapping assembly 17 to extend outside the sheath, and themapping assembly 17 returns to its original shape due to theshape-memory of the support member 24. The mapping assembly 17 is theninserted into a pulmonary vein or other tubular region (such as thecoronary sinus, superior vena cava, or inferior vena cava) so that theouter circumference of the generally circular main region 39 of theassembly is in contact with a circumference inside the tubular region.Preferably at least about 50%, more preferably at least about 70%, andstill more preferably at least about 80% of the circumference of thegenerally circular main region is in contact with a circumference insidethe tubular region.

[0042] The circular arrangement of the electrodes 36 permits measurementof the electrical activity at that circumference of the tubularstructure so that ectopic beats between the electrodes can beidentified. The size of the generally circular main region 39 permitsmeasurement of electrical activity along a diameter of a pulmonary veinor other tubular structure of or near the heart because the circularmain region has a diameter generally corresponding to that of apulmonary vein or the coronary sinus. Additionally, because the mainregion 39 preferably does not form a flat circle, but instead issomewhat helical, as shown in FIG. 4, it is easier for the user to guidethe mapping assembly 17 into a tubular region.

[0043] If desired, two or more puller wires can be provided to enhancethe ability to manipulate the intermediate section. In such anembodiment, a second puller wire and a surrounding second compressioncoil extend through the catheter body and into an additional off-axislumen in the intermediate section. The first puller wire is preferablyanchored proximal to the anchor location of the second puller wire.Suitable designs of catheters having two or more puller wires, includingsuitable control handles for such embodiments, are described, forexample, in U.S. patent application Ser. Nos. 08/924,611, filed Sep. 5,1997; 09/130,359, filed Aug. 7, 1998; 09/143,426, filed Aug. 28, 1998;and 09/157,055, filed Sep. 18, 1998, the disclosures of which areincorporated herein by reference.

[0044] The preceding description has been presented with reference topresently preferred embodiments of the invention. Workers skilled in theart and technology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention.

[0045] Accordingly, the foregoing description should not be read aspertaining only to the precise structures described and illustrated inthe accompanying drawings, but rather should be read consistent with andas support to the following claims which are to have their fullest andfair scope.

1. A method for mapping electrical activity within a tubular region ofor near the heart having a inner circumference, the method comprising:inserting into the heart a distal end of a mapping catheter comprising:an elongated tubular catheter body having an outer wall, proximal anddistal ends, and at least one lumen extending therethrough, and amapping assembly comprising: a tubular structure comprising a pre-formedgenerally circular main region generally transverse and distal to thecatheter body and having an outer circumference, wherein the tubularstructure comprises a non-conductive cover over at least the main regionof the mapping assembly, and a plurality of electrode pairs, eachcomprising two ring electrodes, carried by the generally circular mainregion of the mapping assembly; contacting the outer circumference ofthe generally circular main region with the inner circumference of thetubular region; and mapping the electrical activity within the tubularregion with the electrodes along the generally circular main region. 2.The method according to claim 1, wherein the mapping assembly furthercomprises a support member having shape-memory disposed within at leastthe main region of the mapping assembly.
 3. The method according toclaim 1, wherein the mapping assembly further comprises a generallystraight distal region distal to the main region, the generally straightdistal region having an atraumatic design to prevent the distal end ofthe mapping assembly from penetrating tissue.
 4. The method according toclaim 1, wherein the mapping assembly further comprises a generallystraight proximal region attached to the catheter body and a transitionregion connecting the proximal region and the main region.
 5. The methodaccording to claim 1, wherein the generally circular main region has anouter diameter ranging to about 10 mm to about 25 mm.
 6. The methodaccording to claim 1, wherein the generally circular main region has anouter diameter ranging to about 12 mm to about 20 mm.
 7. The methodaccording to claim 1, wherein the number of ring electrode pairs alongthe generally circular main region ranges from about six to aboutfourteen.
 8. The method according to claim 1, comprising ten ringelectrode pairs along the generally circular main region.
 9. The methodaccording to claim 1, wherein the ring electrode pairs are approximatelyevenly spaced around the generally circular main region.
 10. The methodaccording to claim 1, wherein the distance between two ring electrodesof each ring electrode pair is less than about 3 mm.
 11. The methodaccording to claim 1, wherein the distance between two ring electrodesof each ring electrode pair is less than about 2 mm.
 12. The methodaccording to claim 1, wherein the distance between two ring electrodesof each ring electrode pair ranges from about 0.5 mm to about 1.5 mm.13. The method according to claim 1, wherein at least some of the ringelectrodes of the electrode pairs have a length ranging from about 0.4mm to about 0.75 mm.
 14. The method according to claim 1, wherein onering electrode has a length longer than the length of the other ringelectrodes.
 15. The method according to claim 1, wherein one ringelectrode has a length ranging from about 1 mm to about 1.5 mm and allof the other ring electrodes each having a length ranging from about 0.4mm to about 0.75 mm.
 16. The method according to claim 1, wherein thetubular region is selected from the group consisting of pulmonary veins,the coronary sinus, the superior vena cava, and the inferior vena cava.17. The method according to claim 1, wherein the tubular region is apulmonary vein.
 18. The method according to claim 1, wherein thegenerally circular main region has an outer diameter ranging to about 12mm to about 20 mm.
 19. The method according to claim 1, wherein at leastabout 50% of the outer circumference of the generally circular mainregion is in contact with the inner circumference of the tubular region.20. The method according to claim 1, wherein at least about 80% of theouter circumference of the generally circular main region is in contactwith the inner circumference of the tubular region.
 21. A method formapping electrical activity within a pulmonary vein of a patient, themethod comprising: inserting into the patient a mapping cathetercomprising: an elongated tubular catheter body having an outer wall,proximal and distal ends, and at least one lumen extending therethrough,and a mapping assembly comprising: a tubular structure comprising apre-formed generally circular main region generally transverse anddistal to the catheter body and having an outer circumference, whereinthe tubular structure comprises a non-conductive cover over at least themain region of the mapping assembly, and a plurality of electrode pairs,each comprising two ring electrodes, carried by the generally circularmain region of the mapping assembly; contacting outer circumference ofthe generally circular main region with the inner circumference of thepulmonary vein; and mapping the electrical activity within the pulmonarywith the electrodes along the generally circular main region.
 22. Themethod according to claim 21, wherein the distance between two ringelectrodes of each ring electrode pair is less than about 2 mm.
 23. Themethod according to claim 21, wherein the distance between two ringelectrodes of each ring electrode pair ranges from about 0.5 mm to about1.5 mm.
 24. The method according to claim 21, wherein at least some ofthe ring electrodes of the electrode pairs have a length ranging fromabout 0.4 mm to about 0.75 mm.
 25. The method according to claim 21,wherein one ring electrode has a length longer than the length of theother ring electrodes.
 26. The method according to claim 21, wherein onering electrode has a length ranging from about 1 mm to about 1.5 mm andall of the other ring electrodes each having a length ranging from about0.4 mm to about 0.75 mm.